Here is LA Scoring Strings, the #1 orchestral library as I write this. Please take a listen and compare the two libraries. People seem to like John William's scores for these types of comparison demos.

When installing the VSTi (Shortcircuit OR Sfz player by RGC Audio, now cakewalk) make sure to place it in your DAW's VST folder, so it appears with your other VSTi's. Same goes for the library, as you will need to find it when you try to load up the samples in your DAW. Best of luck!

If you read the description at the author's site it seems he compiled the samples from various free sounds from reputable sources, such as universities and educational establishments that specialise in recording. He used the SFZ player format because it is free, unlike Kontakt which requires the author to pay for approval.

You can open the SFZ player Vsti in ProTools.

The only thing that's lacking is a GUI which would tie all the samples together, like commercial sample libraries. But it works fine as it is and sounds great, especially for the price... Free!!!